Party Configuration

Hello,

I have an IDOC --> SAP PI --> FILE and FILE --> SAP PI --> IDOC scenarios.

FILE system is in another landscape and hence we need to create PARTY in ID.

1) Can I create only one Business Service for FILE (common for Sender and receiver)?

2) I am creating only one PARTY per external system (we have 3 external systems), so we have 3 different Parties. Is this approach correct?

3) Once I create a Party, what should I mention under the Agency, Scheme and Name?

I have seen this blog: /people/shabarish.vijayakumar/blog/2006/09/13/wanna-party , but it mentiones what needs to be done for IDOC --> SAP PI --> FILE scenario. I have a reverse flow also.

Please suggest.

~Thanks.